DE102007023345B4 - Brake system for a pneumatically coupled with a trailer commercial vehicle and method for operating such a brake system - Google Patents

Abstract

A braking system is provided for a commercial vehicle that can be pneumatically coupled to a trailer. The system includes at least one electronic control unit, and a valve device that can be electrically connected by the at least one electronic control unit. The at least one valve device builds up pressure for the trailer braking system when connected, causing the trailer to brake. A throttle is arranged in a trailer control line. The throttle limits a pressure drop at the control inlet of a relay valve in the event of a leakage downstream of the throttle. A method for controlling a brake system is also provided.

Description

The invention relates to a brake system for a pneumatically coupled to a trailer commercial vehicle, with at least one electronic control unit, an electrically switchable by the at least one electronic control unit valve device, wherein in a switching state of the valve device pressure for the trailer brake system is buildable, which causes a braking of the trailer , and a pressure sensor that detects the pressure for the trailer brake system and transmits a corresponding signal to the electronic control unit, wherein the pressure for the trailer brake system can be influenced by the electronic control unit by pulsed switching of the valve device taking into account the pressure detected by the pressure sensor for the trailer brake system ,

The invention further relates to a method for controlling a brake system for a pneumatically coupled with a trailer commercial vehicle, with at least one electronic control unit, an electrically switchable by the at least one electronic control unit valve device, wherein in a switching state of the valve device pressure for the trailer brake system is built up, the causes a brake of the trailer, and a pressure sensor that detects the pressure for the trailer brake system and transmits a corresponding signal to the electronic control unit, wherein the pressure for the trailer brake system of the electronic control unit by pulsed switching of the valve device taking into account the pressure detected by the pressure sensor is influenced for the trailer brake system.

In connection with commercial vehicles, which can be coupled with a trailer, it is known to stabilize the driving behavior by a so-called stretch braking function. The stretch braking function prevents the trailer from reaching a higher speed on downhill slopes than the towing vehicle, since such a situation could ultimately lead to a buckling of the train and thus to a very unsafe driving situation. Such a stretch braking function can be realized in particular by the pulsed driving of valves which influence the brake pressure of the trailer brake system. The pulsed driving, for example, frequency-modulated and, in particular at a constant frequency, carried out pulse width modulated. The actuated valves may in particular be switching valves, which are primarily intended for switching between a ventilating and a venting state, that is, in principle, should not provide a metered pressure supply. By now such switching valves are controlled, for example, pulse width modulated, that can be switched with a certain duty cycle between the ventilating and the venting state, a quasi-continuous pressure metering in the field of controlled compressed air can be achieved. The problem, however, is that a pulsed control of the switching valves leads to extremely high numbers of cycles, thereby the valves are highly loaded and limited in their life.

From the DE 34 44 639 A1 is a motor vehicle pneumatic system with trailer auxiliary brake circuit known. The auxiliary brake circuit is used to actuate the trailer brakes independent of the motor vehicle brakes, for example as a braked brake to prevent buckling (jackknifing) of the vehicle combination containing the motor vehicle compressed air system.

From the DE 197 06 982 A1 is known to modulate the brake pressure for the trailer depending on the brake pressure applied to the towing vehicle and the determined vehicle mass or the determined load of the trailer, z. B. by a pulse-shaped signal.

From the DE 198 57 393 A1 It is known to allow for a trailer to initiate an independent of the towing vehicle braking process of the trailer. There is provided a separate activation of the brake of the trailer vehicle, which is operated by a switch on the dashboard.

The invention has for its object to reduce the burden of switching valves in connection with a provided by pulse width modulation stretch braking function to improve the vehicle stability.

This object is achieved with the features of the independent claims.

Advantageous embodiments of the invention are indicated in the dependent claims.

The invention is based on the generic brake system in that the electronic control unit only allows the pulsed switching to bring about a braking of the trailer with inoperative service brake of the towing vehicle, if a condition exists in which a braking of the trailer despite non-active service brake of the towing vehicle could be useful, and such a bracing braking is requested by a signal generator. The invention thus provides a kind of filter which ensures that there is no unnecessary activation outside of actually desired and useful braked braking phases the switching valves takes place. The switching valves are therefore no longer always when the driver of the commercial vehicle expresses a corresponding request via a signal generator, exposed to a constant pulsed drive, which has a positive effect on the life of the solenoid valves and the brakes. For example, the pulsed control can lead to a variation of the pressure to be influenced in a pulse-width-modulated manner, and the invention is explained in the context of the present disclosure, without limiting the generality, predominantly using the example of pulse width modulation. The mentioned pressure for the trailer brake system may be a control pressure, based on which the actual brake pressure is generated for the trailer brake system.

In particular, it may be provided that the condition corresponds to the presence of at least one of the following states: the vehicle speed is less than a threshold value, the accelerator pedal is not actuated, the engine brakes, the engine does not generate usable torque, a retarder system is active, the vehicle is located on a downhill slope. Such a driving condition is often present during a sustained braking because here the towing vehicle is braked by the engine and the retarder system, while the trailer is not braked. The retarder system and the engine brake are also referred to as retarders. These are often connected by a separate encoder or switch, these switches are usually switched stufbar. Arrangements are also known in which the engine brake can be switched on independently of the retarder system, but usually there is a combined influenceability and a concomitant coordination of the systems with one another. It is often intended to automatically tune the retardation deceleration to the deceleration of a previous service brake application. The signal generator for the draft braking can be provided separately or combined with the encoder for engine braking or retarder braking. It is also possible to provide the manual control unit for an electric parking brake with an additional function, so that the signal for initiating an extensional braking can be generated. The condition for allowing the extensional braking can be coupled on this basis to the characteristic driving conditions of the vehicle. It is possible to consider only one or even several, in particular all of the mentioned driving conditions. For example, it can be prevented that a pulse width modulated control of the switching valves, that is, the solenoid valves, takes place when the vehicle is moving at a high speed, in which no braked braking function should take place. It can also be provided that when the accelerator pedal is actuated a braked braking function is prevented in any case, because it is unlikely that could occur in such a state, a trailer of the towing vehicle. Furthermore, a criterion for allowing extensional braking may be that the engine is braking, as this indicates a typical driving situation that makes judder braking seem reasonable or necessary. Furthermore, it can be checked, in particular via the engine control unit, whether the engine generates a usable positive torque. If this is not the case, then this is a criterion for allowing extensional braking. By combined continuous braking using a retarder system, also a delay of the commercial vehicle can be brought about. If such a retarder system is active, it may be useful to allow an expansion braking. It is also possible to check whether the vehicle is on a slope, this test being based on inclination sensors or navigation data. If this check reveals that there is no gradient, the pulse-width modulated control of the switching valves can also be suppressed. When controlling the draft braking function, the wheel speeds of towing vehicle and trailer as well as the steering angle can also be taken into account. For example, based on a slip comparison between the trailer and the towing vehicle, it can be determined that the trailer is approaching the towing vehicle. The consideration of the steering angle may be useful because at different steering angles, the vehicle is influenced by a bracing braking in different ways. With regard to the handling of the commercial vehicle, it may also be useful to take into account the different load distribution caused by an E-differential on a continuous braking, which is in particular caused by the engine and a retarder. An E-differential is a continuously variable differential for tuning engine acceleration torque to the forces that can be applied to the road surface by the wheels. An E-differential distributes the wheel forces in a meaningful way individually to the different wheels. It is useful, following an endurance braking when accelerating the vehicle by pressing the accelerator pedal, to stretch the train as fast as possible and not let the engine speed fall into a range in which the engine could die under certain circumstances. In this regard, it may be desirable to release the stretch brake prior to transition to re-acceleration of the train, thereby reducing overall component stress. Further attention can be paid to the suspension sensor and air suspension displacement sensors, which, together with the steering angle and slip during cornering, give an indication of the trailer's thrust forces when retarding is activated. In addition, modern vehicles often have an active steering system which can provide steering angle signals to the control electronics during the bracing operation in order to carry out an automatic steering angle correction. On this basis, a bracing braking operation can be terminated early to thereby also reduce the stress on the components and to improve the driving stability. Furthermore, if an active shock absorber control is present, then a transfer of the shock absorber to a higher degree of hardness can be helpful in order to prevent rolling movements and in this way to be able to end a bracing operation more quickly, whereby this also puts a strain on the controlling components, ie the valves and the brakes, lowered and the driving stability is improved.

Usefully, it is provided that the valve device is preceded by a pressure limiter. A pressure limiter is useful because the number of required switching cycles also increases due to the need for more frequent and more sensitive clocking with increasing supply pressure. By the pressure limiter thus an advantageous influence on the life of the valves is achieved.

It can be provided that the valve device is a 3/2-way valve. On this basis, a ventilation and bleeding function can be realized with a single valve.

It can also be provided that the valve device comprises two 2/2-way valves. Then one of the 2/2-way valves is for venting while the other is vented. If none of the valves is actuated, the pressure is maintained, which is due to the critical driving situation during a draft braking very often aerated and vented.

It is possible that the valve device provides the control pressure directly. Such a valve device designed as a solenoid valve must provide a sufficient flow cross-section.

It is also conceivable that the valve device controls a relay valve, which provides the control pressure available. The indirect provision of the control pressure by the pulse width modulated controlled valve device via a relay valve is useful because the pulse width modulated controlled switching valves can then be dimensioned and designed independently of the control pressure required for the draft braking. The pressure pulses are integrated in the control chamber of the relay valve to a mean pressure, which is then supplied as a control pressure specification of the trailer brake system.

According to a preferred embodiment of the present invention, it is provided that the valve device is integrated in a trailer control module which controls the trailer brake system and supplies it with compressed air.

But it is also conceivable that the valve device is integrated in an electropneumatic control unit which controls the parking brake of the towing vehicle and the trailer brake system via a trailer control module pneumatically.

In this context, it is then useful that in a wiring harness of the electropneumatic control unit, which is in communication with a spring-loaded cylinder of the parking brake of the towing vehicle and with a control input of the trailer control module, at least one throttle is provided which at a pressure reduction in the control input of the trailer control module Pressure reduction in the spring cylinder delayed. Since the electropneumatic control unit couples both the control input of the trailer control module and the parking brake cylinder with the compressed air supply, a pressure loss in the trailer control module could cause a sudden collapse of the pressure in all associated lines of the electro-pneumatic control unit, as well as in the area of the spring-loaded cylinder. This would mean that the towing vehicle is suddenly braked by the parking brake. This is prevented by slowing down a pressure reduction in the region of the spring-loaded cylinder by throttling.

Based on this, it can then be provided that an unexpected pressure reduction in the area of the control input of the trailer control module can be detected by the pressure sensor and the pressure in the spring-loaded cylinder of the parking brake can be maintained by switching over a valve. The pressure sensor, which is also used in conjunction with the pulse width modulated control of the valve device, can thus be used to detect an unexpected drop in pressure in the trailer control module and then separate the spring-loaded cylinder by switching a valve device from the pressure sink. In combination with the pressure throttling, the pressure reduction in the spring-loaded cylinder can thus be slowed down independently of switching and pressure detection, and then completely stopped by switching the valve if required.

Usefully, it can be provided that the signal which can be generated by a manually operable signal generator can be supplied to the at least one electronic control unit and, depending on the presence of the signal, the signal Stretch braking function is suppressible. The driver is thus given the opportunity to disable the stretch braking functionality of the commercial vehicle from the outset.

Furthermore, it can be provided that the at least one electronic control unit can be fed with a variable signal which can be actuated manually in various ways, wherein at least one characteristic of the signal depends on the operating mode of the signal generator and the at least one property of the signal influences the braking behavior of the trailer , In particular, an encoder can be provided, which can be operated via different ways. The built-up pressure for the trailer brake can thus be influenced by the encoder path.

It can also be provided that a signal that can be generated by a manually operable signal generator can be supplied to the at least one electronic control unit, wherein the actuation time of the signal generator influences the braking behavior of the trailer. For example, it may be provided that a higher pressure is built up with longer encoder operation.

Usefully, it is furthermore provided that wheel speed sensors are provided whose signals can be supplied to the at least one electronic control unit, and that the vehicle speed used in connection with the condition for permitting pulsed switching of the valve device can be derived from signals of the rotational speed sensors. For example, based on a slip comparison between the trailer and the towing vehicle, it can be determined that the trailer is approaching the towing vehicle. On the part of the towing vehicle, additionally the speedometer signal or data of a navigation system can be consulted as correction values. The use of active wheel speed sensors makes it possible, especially at low speeds, to provide very good processable values, so that a fast stabilization of the vehicle is made possible.

It may further be provided that the trailer brake system has disc brakes. This is particularly useful in combination with active wheel speed sensors, as disc brakes allow a sensitive pressure reduction and improved metering with low hysteresis, especially at low vehicle speeds. Especially in difficult road conditions, such as with grit (U-chips), so an unwanted locking of the wheels can be avoided.

The invention is based on the generic method by the fact that the electronic control unit only allows the pulsed switching to bring about a braking of the trailer with inoperative service brake of the towing vehicle, if there is a condition in which a braking of the trailer despite non-active service brake of the towing vehicle could be useful, and such a bracing braking is requested by a signal generator.

In this way, the advantages and particularities of the brake system according to the invention are also implemented in the context of a method. This also applies to the following particularly preferred embodiments of the method according to the invention.

This is usefully further developed in that the condition corresponds to the presence of at least one of the following conditions: the vehicle speed is less than a threshold value, the accelerator pedal is not actuated, the engine brakes, the engine generates no usable torque, a retarder system is active, The vehicle is on a slope.

Furthermore, it can be provided that an unexpected pressure reduction in the control input of the trailer control module is detected by the pressure sensor and the pressure in the spring-loaded cylinder of the parking brake is maintained by switching a valve.

It is further preferred that a temperature in the trailer brake system is detected and the pressure for the trailer brake system is reduced when a predetermined temperature threshold is exceeded. It is a safety measure that reduces the load on the trailer brake system and valves.

In this context, it can furthermore be provided that a temperature in the area of the trailer brake system is detected and, when a predetermined temperature threshold is exceeded, bracing braking is prevented.

Another safety measure can be taken, namely that a time is detected during which a bracing braking is performed, and that when a predetermined time threshold is exceeded further bracing braking is inhibited. This also prevents possible overloading of the components involved in the draft braking.

It can also be provided that the activity of the service brake of the towing vehicle is monitored during a bracing braking and that upon activation of the service brake of the Towing vehicle is prevented further stretching braking. Stretch braking in the special sense is then no longer necessary since the braking system of the commercial vehicle is activated as a whole and will keep the train in an extended state.

It is particularly useful that the speed of the engine of the commercial vehicle is monitored during an extension braking. This speed monitoring can for example be performed by the engine control unit of the commercial vehicle, with this information is transmitted to the responsible for the draft braking electronic control unit. Such speed monitoring is useful because the stall braking may cause the RPM to drop to an area where engine stalling or stalling is expected in an unfavorable case. This is to prevent, because then all or almost all functional elements of the vehicle go into a back-up mode, for example, by going from an electronic control to a pneumatic control, so that only a very limited functionality of the entire brake system available stands. In critical driving situations this affects the maneuverability.

In this context, it may be useful to lower the pressure for the trailer brake system when the speed falls below a predetermined speed threshold.

Furthermore, it can be provided that when the engine falls below a predetermined speed threshold, the fuel feed rate for the engine of the commercial vehicle is increased.

As a measure against dying of the engine can also be provided that when falling below a predetermined speed threshold of the boost pressure of a turbocharger is reduced.

Furthermore, it is possible for compressed air from a compressed air reservoir to be supplied to a compressed air system of the utility vehicle when the engine of the commercial vehicle falls below a predetermined speed threshold.

A stalling of the engine can also be prevented by a clutch in a drive train of the commercial vehicle disengages at least partially when falling below a predetermined speed threshold.

It may also be provided that, when a predetermined speed threshold is undershot, a transmission of the utility vehicle is transferred to a transmission position with a reduced transmission ratio.

As a further measure against stalling of the engine, it can be provided that when the speed threshold falls below a predetermined speed threshold, the effect of the retarder system of the commercial vehicle is reduced.

It may also be useful to at least partially close a bypass valve arranged between engine displacements of different cylinders of the engine for the purpose of engine braking. By such a bypass valve, compression work is performed during engine braking by allowing overflow of the compressed volume into the intake piston. By closing the bypass valve in the event of an excessive speed drop, the effect of engine braking can be reduced.

Furthermore, it can be provided that a throttle flap in an exhaust gas stream of the engine is transferred from a throttling to a less throttling position.

As has already been described in connection with the brake system according to the invention, the method according to the invention can be usefully developed by supplying the at least one electronic control unit with a signal generated by a manually operated signal generator and suppressing the anti-jackknifing function as a function of the presence of the signal.

It is also useful for the at least one electronic control unit to be supplied with a variable signal generated by a manually actuable signal generator, wherein at least one characteristic of the signal depends on the manner of actuation of the signal generator and the at least one characteristic of the signal influences the braking behavior of the trailer ,

The method according to the invention can also be favorably developed in that the at least one electronic control unit is supplied with a signal generated by a manually operable signal generator, the operating time of the signal generator influencing the braking behavior of the trailer.

It is also possible that wheel speed sensors are provided, the signals of which are supplied to the at least one electronic control unit, and that the vehicle speed used in connection with the condition for permitting pulsed switching of the valve device is derived from signals of the rotational speed sensors.

The invention will now be described by way of example with reference to the accompanying drawings by way of particularly preferred embodiments.

Show it:

1 a part of a brake system according to the invention;

2 a diagram for explaining a pulse width modulated control of a valve device;

3 a block diagram for explaining a first embodiment of a brake system according to the invention;

4 a block diagram for explaining a second embodiment of a brake system according to the invention and

5 a diagram representation for explaining a pulse width modulated control of a valve device.

In the following description of the drawings, like reference characters designate like or similar components.

1 shows a part of a brake system according to the invention. Via a pressure limiter 28 becomes a 3/2-way valve 20 from a compressed air supply 42 Supplied supplied compressed air. The output side is the 3/2-way valve 20 with a trailer control terminal 44 in connection. The output side pressure of the 3/2-way valve 20 is with a pressure sensor 26 detectable. This pressure sensor transmits the acquired information to an electronic control unit 10 , in dependence and in dependence of other conditions, the condition of the 3/2-way valve 20 controls or regulates. To a variable pressure at the trailer control terminal 44 To provide targeted, is the 3/2-way valve 20 controlled pulse width modulated.

2 shows a diagram representation for explaining a pulse width modulated control of a valve device. The upper diagram shows the switching state of the valve device 20 according to 1 , In switching state B is the valve device 20 in its ventilating position, while in the switching state E is the venting position. For example, this is the 3/2-way valves 20 energized in switching state B and energized in switching state E. The lower diagram shows the development of the pressure at the trailer control connection 44 according to 1 depending on the switching states of the 3/2-way valve shown in the upper diagram 20 shown. During phase a, the ratio between aeration time and venting time is adjusted so that an increase in pressure takes place. During phase b, the duty cycle for the switching state is changed in favor of the de-energized shift position so that the pressure at the trailer control port 44 can be held. If the venting switching position still gains a higher proportion of time compared to the ventilating switching position, as is the case in phase c, a pressure decrease takes place. Depending on the implementation of the present invention, the pressure shown in the lower diagram can be a control pressure supplied to the trailer control module, on the basis of which the trailer brake pressure is influenced, or directly the trailer brake pressure. In the latter case, the pressure-holding phase b could be set at, for example, approximately 8.5 bar.

3 shows a block diagram for explaining a first embodiment of a brake system according to the invention. In this example, the pulse width modulated controllable valve device 20 in an electropneumatic control unit 34 integrated, which has both a spring-loaded connection 46 as well as two control connections 48 . 50 that can be coupled to a control input of a trailer control module has. Preferably, the electropneumatic control unit 34 suitable to provide the functions of an electronic parking brake system. The control unit contains this 34 an electronic control unit 14 , which is suitable to control various solenoid valves, namely in the context of the present invention essential as a 3/2-way valve designed valve device 20 as well as a 2/2-way valve 40 , Depending on the switching position of said valve devices 20 . 40 becomes the control input 52 a relay valve 54 driven. The relay valve is working pressure from the compressed air supply 42 over the pressure limiter 28 and a check valve 56 delivered, depending on the control input 52 pending control pressure is forwarded to the spring accumulator connection. Also is a pressure switch 58 provided via which it is detectable whether the spring accumulator port is vented or vented, so whether the parking brake is engaged or released. In the illustrated position of the 2/2-way valve 40 can the spring-loaded connection 46 depending on the position of the 3/2-way valve 20 ventilated or vented. Will the 2/2-way valve 40 switched, so the pressure at the spring accumulator connection 46 held.

Through the interaction of the 3/2-way valve 20 with the 2/2-way valve 40 can also realize a test function for the commercial vehicle, namely by vented spring accumulator connection 46 via the control connection 28 the connected control input of the trailer control module is briefly ventilated. The ventilation this control input entails bleeding the trailer brake system, so that the entire commercial vehicle must be held in this state by the towing vehicle, wherein the vented state of the spring-loaded terminal by switching the 2/2-way valve 40 can be maintained in its pressure holding position.

A:

Geschwindigkeit des Fahrzeugs

B:

Motordrehmoment

C:

Retarderstatusinformation

D:

Lenkwinkel beziehungsweise Raddifferenzdrehzahl

E:

Zustand der Schalter für Gaspedal und Motorbremse

F:

Neigung

G:

Fahrerwunsch-Gebersignal

Another important task is taken over by the 3/2-way valve 20 in terms of the bracing function. By the 3/2-way valve 20 pulse width modulated by the electronic control units 12 . 14 can be controlled, a targeted pressure at the control port 48 provided for the trailer control module. In particular, a braking of the trailer can be carried out independently of the braking of the towing vehicle, so that an emergence of the trailer can be avoided on the towing vehicle. Whether such a bracing braking is allowed, depends on the driving condition of the vehicle. By taking this into account, safety-critical aspects, for example steering maneuvers, can be taken into account, and it can be ensured that a pulse width modulation of the 3/2-way valve 20 only occurs when the stretch brake functionality is actually needed, thereby reducing the life of the 3/2-way valve 20 is greatly increased. Checking whether the pulse width modulation of the 3/2-way valve 20 principle is made dependent on the signals A, B, C, D, E and F. These signals indicate the following driving conditions of the vehicle, or they are derived from these driving conditions, for example by comparisons with threshold values:

A:

Speed of the vehicle

B:

engine torque

C:

Retarderstatusinformation

D:

Steering angle or wheel differential speed

e:

Condition of the accelerator pedal and engine brake switches

F:

Tilt

G:

Driver input sensor signal

The information about these driving conditions can be obtained from various sources. The vehicle speed can be obtained, for example, from the anti-lock braking system or from the tachograph of the vehicle. Also, active wheel speed sensors can be used because their signals are more accurate, especially at low speeds, than that of the tachograph. In addition, speed values of the navigation system can be included as absolute values. The torque of the engine is available, for example, in the context of engine control. For the steering angle or the wheel speed differential wheel speed sensors are available. In principle, the signals can be obtained directly or via a data bus. To detect the inclination of the vehicle is in particular still to be determined that this can be detected by a sensor; However, the inclination information can also be made available by the navigation system.

The discussed and possibly further signals or variables derived therefrom become the control unit 12 entered. This can in particular be a control unit with a watchdog function. A watchdog function is useful because it is in the context of the present invention is a safety-related control function in which a microcontroller and a computer system must be failsafe and at least partially shut down in the event of an error. Such controllers are advantageously redundantly powered, and have a random access memory to store the allowable control and regulation parameters as well as predetermined thresholds, such as a speed threshold, as well as fault conditions. The control unit can be outside the electropneumatic control unit 34 be arranged, or even be integrated into this, in particular in structural unit with the within the electropneumatic control unit 34 illustrated electronic control unit 14 , Depending on the signals A, B, C, D, E and F causes the electronic control unit 12 now the pulse width modulated control of the 3/2-way valve 20 , wherein a pulse width modulated control can be inhibited, in particular, if due to one or more of the information supplied to the control unit is clear that no stretching braking should take place.

The electropneumatic control unit 34 contains another electrically controllable 3/2-way valve 60 , which is equipped as a bistable valve. This solenoid valve 60 supplies the control connection 50 the electropneumatic control unit 34 with compressed air, so that the illustrated electropneumatic control unit 34 a control pressure for the trailer control module optionally based on a monostable valve design, namely via the 3/2-way valve 20 , or a bistable valve design, namely via the 3/2-way valve 60 can provide. The electropneumatic control unit 34 can thus meet various requirement profiles of commercial vehicle manufacturers.

Another useful feature of the electro-pneumatic control unit 34 stands with the throttles 36 . 38 in relationship, in the conduction paths to the control terminals 48 . 50 are provided for the trailer control module. kick for example, at the control terminal 48 an unexpected loss of compressed air, so the throttle 36 Make sure that this does not cause a sudden venting of the spring-loaded connector 46 leads.

4 shows a block diagram for explaining a second embodiment of a brake system according to the invention. In the embodiment shown here, the pulse width modulated controllable valve device is in the trailer control module 32 integrated. This has a supply line connection 62 for the trailer and a trailer brake pipe connection 64 on. The supply of the trailer control module 32 again takes place via a pressure limiter 28 , the pulse width modulated controllable valve device, here two 2/2-way valves 22 . 24 having, is downstream. The control of the valve device 22 . 24 takes place according to the same fundamental principle as already related to 3 was explained. However, the pulse width modulation can take place, for example, with a constant pulse length, wherein for venting the trailer brake line, the first 2/2-way valve 22 pulsed, while the second 2/2-way valve 24 remains de-energized, and for venting the second 2/2-way valve 24 with de-energized first 2/2-way valve 22 pulsed is driven. To hold the pressure both 2/2-way valves remain 22 . 24 de-energized. In the present embodiment, the pressure supply of the trailer brake line via a relay valve 30 , Also, a direct connection of the trailer brake line to the pulse width modulated controllable solenoid valves 22 . 24 conceivable. Furthermore, a 3/2-way valve can be used instead of the 2/2-way valves. With regard to the pressure sensor 26 It should be mentioned that this monitors whether the pressure delivered to the trailer is within a permissible control window, taking into account the specifications A to G. Furthermore, the hysteresis of the system is included. It becomes the continuity of the pressure increase with respect to the tolerances of the relay valve 30 and depending on the specifications A to G considered. The control unit 16 may have an additional electrical connection, via the on the control unit of the trailer, such as the trailer control module 32 , the Bremsbremswunsch is passed electrically.

In connection with 4 is exemplified that the control unit 16 , for example, comparable to the control unit 12 according to 3 can be constructed, another control device 18 may be downstream, such as the trailer control module own controller, which is designed as a slave controller. The control unit 18 For example, it has no CAN interface. The main computing power is provided by the primary controller 16 made, which is designed as a redundant controller with redundant power supply and an EEPROM memory for parameter and threshold value storage and as a fault memory.

The solution with two 2/2-way valves with or without downstream relay valve is also in connection with the integration of the functionality of the invention in the electropneumatic control unit 34 according to 3 possible. Likewise, in such an electropneumatic control unit, as in 3 is shown, a relay valve are connected downstream of a 3/2-way valve.

5 shows a diagram representation for explaining a pulse width modulated control of a valve device. Here are the switch positions of a vent valve, such as the valve 22 according to 4 , and a vent valve, such as the valve 24 according to 4 , and the associated controlled pressure curves, such as the relay valve 30 according to 4 supplied control pressure or the relay valve 30 at trailer brake pipe connection 64 provided working pressure shown. During pressure build-up, the vent valve is on 24 permanently closed while the vent valve 22 pulsed is driven. Consequently, there is a pressure increase. To keep pressure both valves remain 22 . 24 closed. During the pressure reduction phase, the pressure build-up valve remains 22 closed while the vent valve 24 pulsed is controlled and thus its switching position changes periodically.

The features of the invention disclosed in the foregoing description, in the drawings and in the claims may be essential to the realization of the invention both individually and in any combination.

LIST OF REFERENCE NUMBERS

10

control unit

12

control unit

14

control unit

16

control unit

18

control unit

20

valve means

22

valve means

24

valve means

26

pressure sensor

28

pressure limiter

30

relay valve

32

Trailer control module

34

control unit

36

throttle

38

throttle

40

2/2 way valve

42

Air Supply

44

Trailer control port

46

Spring-loaded connection

48

control connection

50

control connection

52

control input

54

relay valve

56

check valve

58

pressure switch

60

3/2-way valve

62

Supply line connection

64

Trailer brake line connection

Claims (37)

Brake system for a commercial vehicle that can be pneumatically coupled to a trailer, with - at least one electronic control unit ( 10 . 12 . 14 . 16 . 18 ), One by the at least one electronic control unit ( 10 . 12 . 14 . 16 . 18 ) electrically switchable valve device ( 20 . 22 . 24 ), wherein in a switching state of the valve device pressure for the trailer brake system is buildable, which causes a braking of the trailer, and - a pressure sensor ( 26 ), which detects the pressure for the trailer brake system and sends a corresponding signal to the electronic control unit ( 10 . 12 . 14 . 16 . 18 ), - the pressure for the trailer brake system from the electronic control unit ( 10 . 12 . 14 . 16 . 18 ) by pulsed switching of the valve device ( 20 . 22 . 24 ) taking into account that of the pressure sensor ( 26 ) is influenced pressure for the trailer brake system, characterized in that the electronic control unit ( 10 . 12 . 14 . 16 . 18 ) the pulsed switching for causing a braking of the trailer when the service brake of the towing vehicle is not active only if there is a condition in which a braking of the trailer could be useful in spite of non-active service brake of the towing vehicle, and such an extension braking is requested by a signal generator , Brake system according to claim 1, characterized in that the condition corresponds to the presence of at least one of the following states: The vehicle speed is less than a threshold, - the accelerator pedal is not actuated, - the engine brakes, The engine does not generate usable torque, - a retarder system is active, - the vehicle is on a slope. Brake system according to claim 1 or 2, characterized in that the valve device ( 20 . 22 . 24 ) a pressure limiter ( 28 ) is connected upstream. Brake system according to one of the preceding claims, characterized in that the valve device is a 3/2-way valve ( 20 ). Brake system according to one of claims 1 to 3, characterized in that the valve device two 2/2-way valves ( 22 . 24 ). Brake system according to one of the preceding claims, characterized in that the valve device ( 20 ) provides the control pressure directly. Brake system according to one of claims 1 to 6, characterized in that the valve device ( 22 . 24 ) a relay valve ( 30 ), which provides the control pressure. Brake system according to one of the preceding claims, characterized in that the valve device ( 22 . 24 ) into a trailer control module ( 32 ), which controls the trailer brake system and supplies it with compressed air. Brake system according to one of claims 1 to 7, characterized in that the valve device ( 20 ) into an electropneumatic control unit ( 34 ) which pneumatically controls the parking brake of the towing vehicle and the trailer brake system via a trailer control module. Brake system according to claim 9, characterized in that in a wiring harness of the electro-pneumatic control unit ( 34 ), which is in communication with a spring-loaded cylinder of the parking brake of the towing vehicle and with a control input of the trailer control module, at least one throttle ( 36 . 38 ) is provided, which delays in a pressure reduction in the control input of the trailer control module pressure reduction in the spring-loaded cylinder. Brake system according to claim 10, characterized in that an unexpected pressure reduction in the region of the control input of the trailer control module by the pressure sensor ( 26 ) is detectable and the pressure in the spring-loaded cylinder of the parking brake by switching a valve ( 40 ) can be held. Brake system according to one of the preceding claims, characterized in that the at least one electronic control unit ( 10 . 12 . 14 . 16 . 18 ) can be fed to a signal which can be generated by a manually operable signal generator and in dependence on the presence of the signal, the stretch braking function can be suppressed. Brake system according to one of the preceding claims, characterized in that the at least one electronic control unit ( 10 . 12 . 14 . 16 . 18 ) can be fed from a manually operable in various ways signal generator producible variable signal, wherein at least one property of the signal on the manner of actuation of the signal generator depends and the at least one property of the signal affects the braking behavior of the trailer. Brake system according to one of the preceding claims, characterized in that the at least one electronic control unit ( 10 . 12 . 14 . 16 . 18 ) can be fed to a signal generated by a manually operable signal generator, wherein the actuation time of the signal generator affects the braking behavior of the trailer. Brake system according to one of claims 2 to 14, characterized in that wheel speed sensors are provided, the signals of the at least one electronic control unit ( 10 . 12 . 14 . 16 . 18 ), and that the vehicle speed used in connection with the condition for permitting pulsed switching of the valve device can be derived from signals of the rotational speed sensors. Brake system according to one of the preceding claims, characterized in that the trailer brake system comprises disc brakes. Method for controlling a brake system for a commercial vehicle pneumatically coupleable with a trailer, comprising - at least one electronic control unit ( 10 . 12 . 14 . 16 . 18 ), One by the at least one electronic control unit ( 10 . 12 . 14 . 16 . 18 ) electrically switchable valve device ( 20 . 22 . 24 ), wherein in a switching state of the valve device pressure for the trailer brake system is buildable, which causes a braking of the trailer, and - a pressure sensor ( 26 ), which detects the pressure for the trailer brake system and sends a corresponding signal to the electronic control unit ( 10 . 12 . 14 . 16 . 18 ), - the pressure for the trailer brake system from the electronic control unit ( 10 . 12 . 14 . 16 . 18 ) by pulsed switching of the valve device ( 20 . 22 . 24 ) taking into account that of the pressure sensor ( 26 ) is influenced for the trailer brake system, characterized in that the electronic control unit ( 10 . 12 . 14 . 16 . 18 ) the pulsed switching for causing a braking of the trailer when the service brake of the towing vehicle is not active only if there is a condition in which a braking of the trailer could be useful in spite of non-active service brake of the towing vehicle, and such an extension braking is requested by a signal generator , A method according to claim 17, characterized in that the condition corresponds to the presence of at least one of the following conditions: The vehicle speed is less than a threshold, - the accelerator pedal is not actuated, - the engine brakes, The engine does not generate usable torque, - a retarder system is active, - the vehicle is on a slope. A method according to claim 17 or 18, characterized in that an unexpected pressure reduction in the region of the control input of the trailer control module by the pressure sensor ( 26 ) is detected and the pressure in the spring-loaded cylinder of the parking brake by switching a valve ( 40 ) is held. Method according to one of claims 17 to 19, characterized in that a temperature in the region of the trailer brake system is detected and when exceeding a predetermined temperature threshold, the pressure for the trailer brake system is reduced. Method according to one of claims 17 to 20, characterized in that a temperature in the region of the trailer brake system is detected and when exceeding a predetermined temperature threshold, a bracing braking is prevented. Method according to one of claims 17 to 21, characterized in that a time is detected during which a stretch braking is performed, and that when exceeding a predetermined time threshold, a further stretching braking is prevented. Method according to one of claims 17 to 21, characterized in that the activity of the service brake of the towing vehicle is monitored during a bracing braking and that upon activation of the service brake of the towing vehicle, a further bracing braking is inhibited. Method according to one of claims 17 to 21, characterized in that the speed of rotation of the engine of the commercial vehicle is monitored during a bracing braking. A method according to claim 24, characterized in that when falling below a predetermined speed threshold, the pressure for the trailer brake system is reduced. A method according to claim 24 or 25, characterized in that when falling below a predetermined speed threshold, the fuel supply rate for the engine of the commercial vehicle is increased. Method according to one of claims 24 or 26, characterized in that when falling below a predetermined speed threshold, the boost pressure of a turbocharger is reduced. Method according to one of claims 24 to 27, characterized in that is supplied to the engine of the commercial vehicle compressed air from a compressed air tank compressed air system of the commercial vehicle when falling below a predetermined speed threshold. Method according to one of claims 24 to 28, characterized in that when falling below a predetermined speed threshold, a clutch in a drive train of the commercial vehicle disengages at least partially. Method according to one of claims 24 or 29, characterized in that when falling below a predetermined speed threshold, a transmission of the commercial vehicle is converted into a gear position with reduced translation. Method according to one of claims 24 to 30, characterized in that when falling below a predetermined speed threshold, the effect of the retarder system of the commercial vehicle is reduced. Method according to one of claims 24 to 31, characterized in that a for the purpose of engine braking between displacements of different cylinders of the engine arranged by-pass valve is at least partially closed. Method according to one of claims 24 to 32, characterized in that a throttle valve is transferred in an exhaust gas flow of the engine from a throttling to a less throttling position. Method according to one of claims 24 to 33, characterized in that the at least one electronic control unit ( 10 . 12 . 14 . 16 . 18 ) a signal generated by a manually operable signal generator is supplied and in response to the presence of the signal, the stretching brake function is suppressed. Method according to one of claims 24 to 34, characterized in that the at least one electronic control unit ( 10 . 12 . 14 . 16 . 18 ) is supplied from a manually operable in various ways signal generator generated variable signal, wherein at least one property of the signal depends on the manner of actuation of the signal generator and the at least one property of the signal affects the braking behavior of the trailer. Method according to one of claims 14 to 35, characterized in that the at least one electronic control unit ( 10 . 12 . 14 . 16 . 18 ) a signal generated by a manually operable signal generator is supplied, wherein the actuation time of the signal generator influences the braking behavior of the trailer. Method according to one of claims 14 to 36, characterized in that wheel speed sensors are provided, the signals of the at least one electronic control unit ( 10 . 12 . 14 . 16 . 18 ), and that the vehicle speed used in connection with the condition for permitting pulsed switching of the valve device is derived from signals of the rotational speed sensors.

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